Hundreds of thousands of people have gathered at the square, the focal point of protests in Egypt, for what they have termed the "Day of Departure".

As the country entered its eleventh day of unrest, mass demonstrations commenced after Friday prayers.

Thousands also gathered in the city of Alexandria, holding up placards and chanting "He must go!" an Al Jazeera correspondent there reported.

Protesters there have said they will march to the city's main train station and stage a sit-in until Mubarak resigns.

Three thousand people also joined demonstrations in Giza.

In Cairo, about 200 Mubarak loyalists had gathered on the 6th of October Bridge, near Tahrir Square, with another 200 below the bridge.

They were chanting pro-regime slogans, and holding up posters of Mubarak.

Our correspondent reported that there was a standoff between about 300 Mubarak loyalists and pro-democracy protesters in the Talaat Harb square, which is located on a street leading to the main protest centre.

People were throwing rocks at one another, and the Mubarak loyalists were eventually driven from the square.

Our correspondents at the scene reported that there were up to five layers of checkpoints at some entrances, with makeshift barricades being put up by pro-democracy protesters.

"The feel here is that today is the final day for Mubarak, it's time for him to go," Gigi Ibrahim, a political activist told Al Jazeera from the square.

"This whole process has been about who is more determined and who is not willing to give up. And everyday [the protesters] get more and more determined," Ibrahim said.

Mohamed Hussein Tantawi, Egypt's defence minister, also visited the square earlier on Friday. He talked with the protesters and other military commanders.

Amr Moussa, Egypt's former foreign minister and current secretary-general of the Arab League, also visited the square.

Mubarak's government has struggled to regain control of a nation angry about poverty, recession and political repression, inviting the Muslim Brotherhood - Egypt's most organised opposition movement - to talks and apologising for Wednesday's bloodshed in Cairo.

Transition government

Protesters chanted 'He must go!'

In a bid to calm the situation, Omar Suleiman, the vice-president, said on Thursday that Muslim Brotherhood and other opposition groups had been invited to meet the new government as part of a national dialogue.

An offer to talk to the Muslim Brotherhood would have been unthinkable before protests erupted on January 25, indicating the gains made by the pro-democracy movement since then.

But sensing victory, they have refused talks until Mubarak goes.

Opposition actors including Mohamed ElBaradei, the former UN nuclear watchdog head, and the Muslim Brotherhood said again that Mubarak, who wants to stay on until elections scheduled for September, must go before they would negotiate with the government.

"We demand that this regime is overthrown, and we demand the formation of a national unity government for all the factions," the Muslim Brotherhood said in a statement broadcast by Al Jazeera.

The government's overture came after Shafiq, the prime minister, apologised for Wednesday's violence and the breakdown in law and order.

Shafiq also said he did not know who was responsible for the bloodshed, blamed by protesters on undercover police.

Mohammed Al-Beltagi, a leading member of Muslim Brotherhood, told Al Jazeera on Friday that his organisation has no ambitions to run for the presidency.

The developments come as the New York Times reports, quoting US officials and Arab diplomats, that the US administration is discussing with Egyptian officials a proposal for Mubarak to resign immediately and hand over power to a transitional government headed by Omar Suleiman, the newly appointed vice-president.

This report, though unconfirmed by the White House, comes after Mubarak's statements on Tuesday this week, where he agreed to give up power in September at the end of his current term.

Mohamed Talaat El-Sadat, brother of the late Egyptian president Anwar El-Sadaat has backed Suleiman for the top post. He told Al Jazeera on Friday that he supported the youth revolution but did not want Egypt to go to civil war.

"We don’t want chaos and call for meeting [the] demands of demonstrators who should stay at Tahrir Square," he said, adding "I expect Mubarak will voluntarily and openhandedly step down and transfer power to Omar Suleiman."

Bloody clashes

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At least 13 people have died and scores were injured over the last two days when Mubarak loyalists launched a counter-revolution on pro-democracy protesters.

The army took little action while the fighting raged in Tahrir Square over the past two days.

However, there was a more visible military presence on Thursday; but this did not prevent new clashes.

The interior ministry has denied it ordered its agents or officers to attack prior pro-democracy demonstrations.

Vice president Suleiman told ABC Television that the government would not forcefully remove protesters. "We will ask them to go home, but we will not push them to go home," he said.

Ahead of Friday's mass protests, eyewitnesses told Al Jazeera that thugs, with the assistance of security vehicles, were readying to attack Tahrir Square. They said protesters were preparing to confront them.

An Al Jazeera correspondent, who spent Thursday night in Tahrir Square, said "the numbers did not die down one bit" through the night.

He added that there was an atmosphere of defiance among all the protesters he had spoken to.

The army's role in shaping events is crucial. Only on Thursday did soldiers set up a clear buffer zone around the square to separate factions after having stood by. That did not prevent new clashes as opposing groups pelted each other with rocks.

Though less numerous than earlier in the week, there were demonstrations on Thursday in Suez and Ismailia, industrial cities where inflation and unemployment have kindled the sort of dissent that hit Tunisia and which some believe could ripple in a domino effect across other Arab police states.